Distance Fallen vs. Stain Diameter
Learners observe how a blood drop in flight continually accelerates and increases in velocity over time. As the drop falls, resistance accumulates. The increase in stain diameter relative to distance of a typical 50 ml drop of blood is represented here. This activity has audio content.
In this learning object the student will learn how to measure a stain and calculate angles of impact. Determining the angle of impact for bloodstains takes advantage of the trigonometric functions (Sine function).
A mathematical relationship exists between the width and length of an elliptical bloodstain which allows for the calculation of the angle of the impact for the original spherical drop of blood.
Given well formed stains we can accurately measure the width and length by simply dividing the stain along it’s major and minor axis. The opposite halves would be generally equal to each other which aids in establishing the impact angle.